Shrinking Great LakesBy Cynthia Kirk
This is Bill White with the VOA Special English ENVIRONMENT REPORT.
North America's five Great Lakes are the world's largest group of freshwater lakes. The lakes are named Superior, Michigan, Huron, Erie and Ontario. They stretch from the midwestern state of Minnesota to the eastern state of New York.
Of the five lakes, only Lake Michigan lies completely within the United States. The other four lakes are shared by the United States and Canada. They also form part of the border between the two countries. A Nineteen-Oh-Nine treaty provides for joint control of the lakes by the two countries.
The Great Lakes form the most important inland waterway in North America. The five lakes and their canals are important to the economies of the United States and Canada.
Scientists say several years of warm, dry weather are lowering water levels in all five Great Lakes. Water levels have dropped fastest in Lake Michigan, Lake Huron and Lake Erie. But Lake Superior and Lake Ontario are also lower than average. By the end of summer, the lakes are expected to be at their lowest levels in the one-hundred-twenty years that records have been kept.
One reason for the lower lake levels is less rain and snowfall in the northern United States and eastern Canada during the past two years. Lake Superior gets most of its water from melting snow. Most of that water then flows to the other Great Lakes. Also, warmer temperatures have caused more water in the lakes to evaporate.
Officials say low water levels in the Great Lakes affect shipping, fishing, the travel industry and the environment.
Many areas are dealing with the problem by digging into the soft lake bottom near their shores. This process called dredging is designed to make the water deeper so ships can operate.
But dredging has led to concerns from some environmentalists. They say particles from the lake bottom could be harmful to plants and animals. And they say dredging could endanger water supplies for communities that have water-intake pipes near their shores.
Officials in the United States and Canada will try to control water levels this year by reducing the amount of water permitted to flow out of Lake Superior and Lake Ontario. However, officials say they do not expected the lakes to return to normal levels for at least a year.
This VOA Special English ENVIRONMENT REPORT was written by Cynthia Kirk. This is Bill White.